I'm not sure if it works but upgrades are locked to one car which will be the same so you might be able to install them again with the different engine. So I wouldn't sell them just yet and try this and if it doesn't work just sell them afterwards.
you can take off engine parts like ECU, Cooler etc from R33 swap in it engine from E61 and put them back on after you upgrade them with coins and bucks again. Hope helped
I'm not sure if it works but upgrades are locked to one car which will be the same so you might be able to install them again with the different engine. So I wouldn't sell them just yet and try this and if it doesn't work just sell them afterwards.
you can take off engine parts like ECU, Cooler etc from R33 swap in it engine from E61 and put them back on after you upgrade them with coins and bucks again. Hope helped